The invention relates to methods and apparatus of heating glass batch material and more particularly to preheating glass batch material in pellet form prior to feeding the pellets to a glass melting tank or furnace.
Raw materials used to form glass, known as glass batch material, are available in divided or powdered form and must be fed to a tank or furnace in which they are melted as a substantially homogeneous mixture so as to ensure that all the components can interact with one another to form homogeneous molten glass. In order to conserve energy and improve the rate at which the batch material is melted in the tank, the glass batch material can be formed into pellets prior to being fed to the tank or furnace and these pellets may be preheated, for example, using waste gases from the tank or furnace. In the operation of large melting tanks such as are used to feed molten glass to a flat glass forming line operating at loads in the region of 2000 to 5000 tons per week, there is a need to provide a continuous feed of preheated pellets. It is preferable to use a flow system with the pellets flowing in the opposite direction to the heating gases in order to handle the volume of pellets needed to maintain the desired feed of molten glass to the forming process. It is desirable to arrange for the heating gas to heat the pellets with an even distribution of heat transfer so that the pellets fed to the glass melting tank are at a substantially uniform temperature and thereby cause a consistent rate of melting within the tank and partially melted pellets are not carried down the melting tank.
It is an object of the present invention to provide improved apparatus and methods of preheating glass batch material in pellet form prior to feeding the pellets to a glass melting tank.